Whisking: Development of an "active touch" system. A central goal of neuroscience is understanding sensorimotor integration-how the brain processes information and uses it to control movements. Much of this information is acquired actively, using "mobile sensors" such as the human fingers or the rodent whiskers, which scan the environment, transforming the spatial properties of objects into spatio-temporal patterns of neural activity. Such scanning patterns are among the most complex movements generated by the somatosensorimotor system. However, we have little information about how such patterns are acquired during development. We suggest that the normal development of "active touch" systems is contingent upon the occurrence, during development, of associations between the animal's own movements and the sensory inputs generated by those movements. We hypothesize that perinatal manipulations of such sensorimotor linkages will selectively impact upon behavioral tasks dependent on "active touch". To test the hypothesis we use rodent whisking as a model of "active touch". We use perinatal injections of Botulinum toxin to reversibly block afference generated by the animal's own whisking movements, leaving intact other sources of vibrissal afference (whisking deprivation). We use neonatal optic nerve section to increase dependence upon vibrissal inputs (whisking supplementation). In adult animals, we examine treatment effects upon a variety of vibrissa-mediated behaviors, and upon the receptive field organization of cortical vibrissal neurons. These studies should advance our understanding of processes mediating developmental plasticity in the somatosensorimotor system.